Microbial drivers of soil C:N:P stoichiometry dynamics during ecological restoration in sandy ecosystems

Abstract

Soil microbes drive plant diversity and productivity in terrestrial ecosystems and are directly involved in plant nutrient acquisition and soil nutrient cycling. However, the microbiological mechanisms of soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) stoichiometry during vegetation restoration in sandy land remain unclear. This study investigated the ecological stoichiometric characteristics of SOC, TN, and TP in semi-arid degraded sandy land and the underlying mechanisms using space for time substitution for sites in different stages of vegetation restoration: mobile dunes (MD), semi-mobile dunes (SMD), semi-fixed dunes (SFD), fixed dunes (FD), and sparse forest grassland (SFG). SOC, TN, and TP contents increased significantly with restoration of sandy vegetation, indicating a gradual improvement in soil quality. The increase of SOC:TP and TN:TP with vegetation restoration indicated that the accumulation rate of carbon and nitrogen was faster than that of phosphorus, and phosphorus became a key limiting element after vegetation restoration. Decreased SOC:TN indicated accelerated organic matter decomposition and enhanced nitrogen mineralization. In the MD and SMD stages, carbon, nitrogen and phosphorus lacked stable organic carriers (such as humus), resulting in no significant correlation between SOC, TN and TP contents. However, with the restoration of vegetation in sandy land, the significant correlation between SOC and TN was enhanced, and the correlation between TN and TP was stronger than that between SOC and TN, SOC and TP. The enhancement of extracellular enzyme activities driven by precipitation prompted a succession of microbial communities from copiotrophic (dominated by Ascomycetes) to oligotrophic (dominated by Acidobacteria) during vegetation restoration in sandy land. We found that vegetation restoration and precipitation shape nutrient dynamics via their influence on microbial and extracellular activity. This has important implications for developing effective strategies to mitigate desertification and its impact on global ecosystems.